[PATCH v2 01/20] make sure that DNAME_INLINE_LEN is a multiple of word size

Al Viro
2025-01-16T05:23:20Z

... calling the number of words DNAME_INLINE_WORDS.

The next step will be to have a structure to hold inline name arrays
(both in dentry and in name_snapshot) and use that to alias the
existing arrays of unsigned char there. That will allow both
full-structure copies and convenient word-by-word accesses.

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/dcache.c | 4 +---
include/linux/dcache.h | 8 +++++---
2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index b4d5e9e1e43d..ea0f0bea511b 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2748,9 +2748,7 @@ static void swap_names(struct dentry *dentry, struct dentry *target)
/*
* Both are internal.
*/
- unsigned int i;
- BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long)));
- for (i = 0; i < DNAME_INLINE_LEN / sizeof(long); i++) {
+ for (int i = 0; i < DNAME_INLINE_WORDS; i++) {
swap(((long *) &dentry->d_iname)[i],
((long *) &target->d_iname)[i]);
}
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index bff956f7b2b9..42dd89beaf4e 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -68,15 +68,17 @@ extern const struct qstr dotdot_name;
* large memory footprint increase).
*/
#ifdef CONFIG_64BIT
-# define DNAME_INLINE_LEN 40 /* 192 bytes */
+# define DNAME_INLINE_WORDS 5 /* 192 bytes */
#else
# ifdef CONFIG_SMP
-# define DNAME_INLINE_LEN 36 /* 128 bytes */
+# define DNAME_INLINE_WORDS 9 /* 128 bytes */
# else
-# define DNAME_INLINE_LEN 44 /* 128 bytes */
+# define DNAME_INLINE_WORDS 11 /* 128 bytes */
# endif
#endif

+#define DNAME_INLINE_LEN (DNAME_INLINE_WORDS*sizeof(unsigned long))
+
#define d_lock d_lockref.lock

struct dentry {
--
2.39.5